Aqueous highly alkaline hair relaxer (straightener) compositions are known in the art in the form of alkaline, oil-in-water emulsions which derive their chemical activity from either (1) alkali metal hydroxides, (2) quaternary ammonium hydroxides, or (3) guanidine hydroxide dissolved or suspended in the water phase of these hair-treatment compositions such that the pH values of these emulsions are in the range of from 12 to 14 ("highly alkaline"). It is widely and generally accepted that it is the hydroxide ion, which is the alkaline chemical species common to all three of the above classes, that is the essential active ingredient in these "strong base" relaxers. It has been proven that hydroxide ions, when inside the cortex of the hair, readily extract acidic alpha protons from the cysteine moieties of hair keratin leading to reversible beta elimination of alkyl disulfide (opening of cross-links) with the concomitant formation of dehydroalanine. As these crosslinks continuously open and reform, the curly hair is relaxed to a permanently straight configuration.
Although it is the hydroxide anion which is responsible for initiating the chemical reactions within the hair shaft which lead to straightening, it is the cation with which the hydroxide is associated that distinguishes the various known highly alkaline relaxer types from each other. Prior to 1979, one-component ("no-mix") highly alkaline hair relaxer compositions deriving from either sodium or potassium hydroxides were known. In 1979, a mix-type "no-lye" relaxer containing guanidine hydroxide was introduced. A no-lye relaxer is one that does not contain sodium or potassium hydroxide. Because guanidine hydroxide is not stable for long periods in aqueous solutions, it must be prepared fresh just prior to using. Guanidine hydroxide is generally prepared by mixing an inorganic alkaline earth hydroxide with an aqueous solution of a salt of the strong organic base guanidine, where the anion of the salt is capable of being precipitated by the cation of the alkaline earth hydroxide. In commercially available products of this type, the guanidine hydroxide is generally prepared using calcium hydroxide and guanidine carbonate.
Two-component systems for the preparation and use of guanidine hydroxide relaxers are well documented in the patent literature, as disclosed, for example, in U.S. Pat. No. 4,304,244. The first component comprises a viscous cream base containing calcium hydroxide and the second component, known as an activator, comprises an aqueous solution of guanidine carbonate. The two components are combined to form an activated cream containing guanidine hydroxide. U.S. Pat. No. 4,304,244 discloses a two-component composition, and states that one or both of the components may be in the form of an aqueous solution, or both components may be in a non-aqueous form with water additionally added to the admixed components. The patent states that when a two-component system is used, the individual components may vary from a solid component to a very dilute solution or dispersion. The patent states that it is decidedly preferred that the hydroxide component and guanidine salt be packaged as separate components, especially with each component in the form of an aqueous solution, as the resulting mixing of the components is greatly facilitated thereby. All of the examples which employed a two-component system used a cream base containing an alkaline earth metal hydroxide (e.g., calcium hydroxide) and a guanidine carbonate solution in a weight ratio of at least 70% cream base to 30% guanidine carbonate solution.
The volume of liquid activator in the commercially available two-component systems is typically 50 to 80 ml, and is contained in a container or bottle with a narrow mouth to facilitate pouring. The volume of the cream base is generally 200 to 220 ml and is contained in a wide-mouth container to facilitate the stirring process when the liquid activator is poured into the cream base. Both the cream base and the liquid activator have a significant amount of water present.
The liquid activator contains a sufficient amount of water to ensure that the guanidine carbonate is completely dissolved in the activator. The guanidine carbonate is typically present in the activator in a high concentration of 20 to 30% by weight. The cream base, which is an oil-in-water emulsion, typically contains about 40 to 60 weight percent water, and 4 to 7 weight percent calcium hydroxide. The calcium hydroxide generally is present in a molar excess with respect to the guanidine carbonate. The cream base to liquid activator weight ratio is generally at least about 3-to-1 to 6-to-1. The cream base and liquid activator each have a density of about 1, and thus the cream base to liquid activator volume ratio also is generally about 3-to-1 to 6-to-1.
The activator to be added to the cream base contains a significant amount of water in relation to the total amount of water present in the two components, and the cream base is usually formulated to be viscous so that when the additional water from the liquid activator is added to the cream base, the resulting admixed relaxer will have a manageable consistency and will not become runny. The viscous cream base, in itself, however, is thick and difficult to stir. Moreover, the large difference in rheologies between the cream base and liquid activator makes it more difficult to uniformly mix the activator with the cream base. Mixing times for conventional two-component systems are typically long, on the order of two to four minutes, depending on the age of the cream base.
A food coloring is sometimes added to the activator so as to provide the consumer with visual feedback on the degree of mixing of the liquid activator and the cream base. For example, if red food coloring is added to the liquid activator, when mixed with a white cream base, the consumer will be directed to achieve a uniform pink color.
The two-component systems currently in use present a number of problems for the consumer. The existing two-component systems are most accurate when the user mixes all of the cream base supplied in the container with all of the concentrated liquid activator supplied in the bottle. Because these components are pre-measured to close tolerances by the manufacturer, the thorough mixing of full measures by the consumer results in relaxers whose chemical strengths are those designed by the manufacturer for different hair textures and types. Even when full measures are used, however, any accidental spillage (typically by splashing during mixing) of even a small amount of the concentrated liquid activator will yield a mixed relaxer having a lower strength than intended.
Another problem arises when the consumer uses only a portion of the relaxer kit at one time while saving the remaining product for later use. After having a relaxer treatment and as new hair grows, the consumer must relax the new growth to maintain the hairstyle. Because these touch-ups seldom require the entire amount of relaxer in a kit, the consumer typically will measure out and mix half of the contents of both the relaxer base cream container and the activator bottle. Then, the consumer saves the remaining unmixed components and uses them later for a second touch-up.
In preparing a relaxer using less than the full contents of a kit, the consumer generally relies on estimates which the consumer makes of half measures, from pre-drawn lines on the cream base container and the liquid activator bottle. For example, the consumer must first measure out one half the contents of the cream base. In some relaxers this is accomplished by measuring out a predetermined number of level scoops. Of course, if the consumer does not use the scoop and attempts to estimate one half the contents of the cream base, there is a large likelihood of error. Even if the consumer is careful in measuring out the indicated number of scoops, the scoops may not be level, and the scoop may not be entirely emptied before refilling successive scoops.
Once having measured the one-half amount of cream base, the consumer must then measure out one half of the liquid activator containing guanidine carbonate. Such commercially available liquid activators typically contain a "half line" on the side of the bottle so that the consumer will know what is the half contents amount. Again, consumer errors in measuring amounts of activator are also common and difficult to avoid. Moreover, the half line is not always accurately placed on the bottle by the manufacturer, and the quantity of activator actually filled into the bottle may be over or under the intended amount due to mal-adjustment or malfunction of the high-speed filling equipment.
The problem arises that unless the consumer is extremely diligent in measuring out the one-half amounts of base and activator, the final guanidine hydroxide concentration in the mixture will greatly vary depending on whether the measured amounts are over or under the one-half target amount. It has been determined that consumer errors from measuring the base and/or activator can easily result in fluctuations of .+-.10% in the volume of cream base and .+-.10% in the volume of activator employed, resulting in fluctuations in guanidine hydroxide concentrations of .+-.10 percent or more, when the target amounts are half of the container contents. Measuring errors can be much greater when the estimated targets are other than half contents or when spillage occurs. These measuring errors of .+-.10% or more can lead to wide variations in strength which can yield poor results such as ineffective relaxing (e.g., the hair does not relax as much as it should) and premature reversion, when the concentration of guanidine hydroxide is too low, or excessive side effects such as scalp irritation, hair damage and hair breakage to the consumer, when the concentration of guanidine hydroxide is too high.
Typically, the cream base component of the two-component relaxer contains an excess of calcium hydroxide so that the reaction of the guanidine carbonate is driven to completion. It is therefore the amount of guanidine carbonate added to the cream base and the total volume of the final mixture that determines the concentration of the guanidine hydroxide in the product when it is applied to the hair. Measuring errors of components on the part of the consumer can greatly alter the concentration of guanidine hydroxide in the admixed product resulting in insufficient relaxation or damage from overprocessing.
In addition to these errors in measuring the amount of liquid activator and cream base, errors are also introduced when the two components are mixed together. In order to obtain a uniform concentration of guanidine hydroxide in all portions of the relaxing mixture, the consumer must thoroughly mix the measured amount of activator and cream base.
It has been observed that consumer errors in the mixing step are also common and difficult to avoid. For example, if the consumer mixes the activator with only the top portion of the cream base, without diligently mixing the contents at the bottom of the cream base container, the concentration of guanidine hydroxide at the top portion of the container will be significantly higher than at the bottom portion of the container. The concentration of guanidine hydroxide at the top portion can vary significantly from that designed by the manufacturer, and can be, for example, as much as two times greater than that designed by the manufacturer. The insufficient mixing by the consumer creates a concentration gradient in the admixed relaxer. Thus, the first half of the relaxer placed on the hair will be much stronger than the bottom half of the relaxer placed on the hair. This results in uneven relaxing and possibly damage to the hair.
U.S. Pat. No. 5,068,101 discloses a two-component system in which one component is an aqueous solution of about 25 to about 30 weight percent guanidine carbonate which serves as the liquid activator, and the other component contains about 4 weight % to about 7 weight % calcium hydroxide emulsified in a cosmetic cream base. About 3.5 to about 6 parts by weight of the cosmetic cream base are mixed with one part by weight of the activator to provide the guanidine hydroxide hair relaxer. U.S. Pat. No. 5,077,042 discloses a conditioning activator which is substantially a liquid comprising a relatively strong organic base and a highly alkaline, no-scalp-barrier- necessary, no-lye cosmetic cream containing calcium hydroxide.
These patents disclose the possibility that guanidine carbonate may be included in the emulsion of the cream base and calcium hydroxide may be added in the form of an aqueous suspension just before use. U.S. Pat. No. 5,077,042 describes this approach as being impractical, and states that the amount of calcium hydroxide required for the reaction would be difficult to suspend in liquid form and would likely result in a non-uniform reaction mixture which would not relax the hair properly. These patents do not disclose any example where the guanidine carbonate is in a cream base and the calcium hydroxide is in an aqueous suspension. These patents do not discuss the problem of consumer measuring and mixing errors.
As a result, these patents do not provide the consumer with a product which does not have the problems of variation in guanidine hydroxide concentration when mixed by the consumer.
Other problems associated with liquid activators include the possibility of spilling and splashing, which can affect the amount of activator that is added to the cream base. Spillage can cause stains, particularly if food coloring is present in the liquid activator.
Another problem in the art is the potential toxicity of the guanidine carbonate solution used to activate the relaxer cream. The relative toxicity of guanidine carbonate is well established in the literature. Currently, the guanidine carbonate solution used in a two-component relaxer is packaged in a child-resistant bottle to prevent accidental ingestion. However, given the volume of the solution (from 50 ml to 80 ml), it is possible that the entire contents of a bottle could be swallowed. Therefore, the potential for accidental ingestion and poisoning based on the small amount of liquid guanidine carbonate remains a problem.
Food coloring has been added to the activator in order to indicate the degree of mixing between the cream base and the activator. However, such a conventional type of indicator does not indicate that the guanidine carbonate has reacted with the calcium hydroxide. It merely shows the extent that the liquid activator has been physically mixed with the cream base.
Another problem in the art is that ammonia is formed over time in the guanidine carbonate aqueous liquid activator component due to the hydrolysis of the guanidine carbonate. The formation of ammonia in the guanidine carbonate aqueous liquid activator component causes an undesirable odor. Thus, the liquid activator itself is inherently unstable and has a relatively limited shelf-life.
A still further problem in the art is that relaxers are often irritating to the scalp of the user. When a consumer is also color treating the hair, which is also irritating to the scalp of the consumer, the consumer must wait for several weeks after the relaxer treatment to color the hair (and vice versa) in order to avoid further irritation.